Cinematographic apparatus



April 21, 1925.

M. A. J. HARPER GINEMATOGRAPHiC APPARATUS Filed Aux. 10, 1921 Fig.1.

Patented Apr. 21, 192.5.

UNITED STATES MARTIN ALBERT JOHN HARPER, OF LONDON, ENGLAND.

CINEMATOGRAPHIC APPARATUS.

Application filed August 10, 1921.

To all 1071 cm it may concern.

Be known that I, MARTIN ALBERT J OHN HARPER, a subject of His Majesty the King of Great Britain, residing at 2 St. Stephens Square, Bayswater, London, England, have invented certain new and useful Improvements in or Relating to Cinematographic Apparatus, of which the following is a specification, reference being had therein to the accompanying drawing.

This invention relates to cinematographic apparatus of the kind in which light concentrated on an opaque film is reflected therefrom through the projecting lens onto the screen, and has for its chief object to provide improved apparatus of this kind whereby the pictorial image thus projected onto the screen will be brilliant and evenly illuminated and entirely free from any image of the illuminant.

According to my invention, I concentrate a beam or pencil of light on the opaque film by means of an optical system comprising an illuminant, such for example as an incandescing filament electric lamp filled with an inert gas; a spherical reflector behind the same; a condenser in front of the illuminant; and a bi-convex lens in front of the condenser at about its focal point; these elements of the optical system being arranged in any suitable manner so as to be relatively adjustable for focussing purposes. By means of this optical system I produce by suitable focussing a brilliant and evenly illuminated patch of light on the film free from any image of the illuminant; and by so arranging the optical system that the beam of light falls obliquely on the film, an oval patch of light is produced thereon which will readily cover the standard sized picture (lx%) although the diameter of the incident beam of light may be less than the diagonal of the picture.

If considered desirable, two oblique beams of light may be directed onto the picture to be reflected, the beams being preferably oppositely and symmetrically disposed and the apparatus used for originating each beam of light being of similar construction.

Since opaque films cannot be turned back to front as can transparent films, I may avoid the necessity for reverse printing of the opaque film in order to obtain a correct side-forside presentation of the picture projected onto the screen, by the use of a reversing prism in. conjunction with the above Serial No. 49 1,087.

described optical system, through which prism the light rays reflected from the opaque film pass onto the screen. The said prism may be arranged either between the opaque film and the projecting lens, or between the said lens and the screen which latter would preferably be in a plane at right angles to that of the film.

To avoid loss of light which may occur owing to emergence of light rays through the reflecting surface of the prism, I prefer to silver the said reflecting surface, or apply a suitable reflecting medium thereto.

I will now describe a manner of carrying my invention into effect having reference to the annexed drawings in which similar reference numerals refer to corresponding parts in all the figures, and wherein Fig. l is a more or less diagrammatic plan view showing cinematographic apparatus in accordance with my invention. Parts not necessary for the proper comprehension of the invention are omitted.

Figs. 2 and 3 are diagrams showing alternative arrangements of the reversing prism.

1 is the opaque film to which intermittent motion may be imparted in the customary or any suitable manner. 2 is the usual gate, 3 a feed sprocket, 4 the projecting lens and 5 the shutter, all of which may be of the ordinary or suitable construction.

A is the optical system for concentrating a beam or pencil of light upon the opaque film and producing a brilliant and evenly illuminated patch of light free from image of the illuminant on the picture to be refiected.

This optical system comprises a suitable box or casing 6 containing the illuminant which may conveniently consist of an electric lamp of thetype comprising a bulb 7 filled with an inert gas and having suitable incandescing filaments 8 therein; a spherical reflector 9, a condenser 10; and a bi-convex lens 11 at about the focal point of the con denser. Thesaid illuminant, reflector, condenser and lens are arranged in any suitable manner so as to be relatively adjustable for focussing purposes. The filaments 8 shown are of the known type consisting of spaced parallel spiral filament coils.

As will. be seen clearly in Fig. 2 the said optical system is so arranged as to com-ere trate a beam of light ol'iliquely on the film 1, and produce thereon an oval patch of light which will readily cover the standard I n'bot-h: arrangements the function of the spri'sm; 12 is; to reverse-the image projected -.onto the screen, thusgiving a correct sidetor-side presentation-of the picture on the size picture, although the diameter of the incident-pencil of light may beless than the diagonal of the picture. The film 1 should a temporary screen; as by removing or ole-t scu'r-ing the reflector -9, removing the lens 11, andfocussing the-anterior light rays ona cardor like temporary screen, placed at about the positionotthe lens 11, so as to form an 'image of 'the filament-s 8- thereon;

then placing the spherical reflector in posil'flOlLiLnCl KlHIStIIIg- H so as to br1ng-theposterionrays-to a focus on the card, forming a co-equal ima-ge otthe filaments 8" thereon interlaced wither s-uperposedupon the im age ot-the filaments formed by the anterior rays.- into place and an-evenly illuminated-patch 'l he bi-convexdens'11 is then fitted of-light will then be formed on-the picture toabe .proj'eetedi by reflection, and since the filmi '1 is @1101; at the image point of the-lens 11 thesaidpatchot uniform light will be "freefromiany imageot the illuminant, and the picture whenprojected on the screen by theusual;projection dens: 1 will be clearlydefinedthereon; Reterring to Figs. 1 and 2, 12 1s a reversingapr ism mounted 111K211 suitable carrier 13 behind theprojecting "lens l, between the latter. and the film, so that the liglit rays reflectedfromrthe' filni 1 will enter thisprismand be deflected-thereby through, the'pro- 1 ectmgdens. lgas :clearly seen ml; 2.,

Or, altemiatlvely, thesald prism may be suitably mountedi in iront 0f the projecting lens= -1-.i'between the latter and the'screen as showniinsthediagram Fig; 3', instead of behind the pro ecting lens as above described.

latter.

Hie-reflecting surface 14. of the :prism is preferably silveredyorhas a suitable reflecting mediumapplied thereto, to avoid loss of=lightby 1 emergence of light rays through thesaid reflecting surface. y

Ifiamaware that-an optical system comprising an: llllimllltllt, a spherical reflec- .tor, a condenser, and a bi convex lens at about the focal point of. the latter, is not n0vel, ;per:se, but soltar-as I am aware such an optical combination has not been heretofore usedvin accordance With the provisions otthese improvements and for the produc itionof a brilliant and evenly illuminated patclrot light on aniopaque filmiin cinematographic I apparatus.

lVha-t I claim and desire to secure by Letters Patent of the United States is 1- 1. In a cinematographic apparatus of the character described, the combination With means fol-feeding an opaque film and a pro jecting'" lens, otanoptical system embodying therein a lamp having a'plurality of spaced filaments, a condenser, a bi-convex lens positioned at about the focal point ofthe condenser and between said condenser andithe feeding means forthefilm-the relative. position of said bi-convex lens and said feeding, means beingsuch as to bring a'fihn upon'said meanswvhere it will not beat the image point-of said lens, and a. spherical reflector positioned with relation to said condenserand' so adjusted as to reflect the image'of the filaments ofthe-lamp through the spaces between or about said filaments,

lamp on the side thereof opposite to said i whereby a-unitorm patch of light tree from the image ot said filaments is directed against the opaque film.

2: In a cinematographic apparatus of the character described, thecombination With means for feeding an opaque film and. a-

projecting lens, of an'optical' system embodying therein a lamphaving a plurality of spaced filaments, acondenser, a bi-convex'lens positionedat about the focal point ot'the con denserandbet'ween said condenser andthe "feeding means for the filin the rela tive positionot saidbi-convex lens and said feedingnmans being 'suchas to bringa-film upon said meanswhere it Will not be atthe image point of said lens, a-revcrsing prism arranged inthe path of thelight r-ayspassing from the film to the screen, and a -spherical refiector positioned with relation to said lamp -on the-side thereofopposite to said condenser 1 and I so adpisted' as to reflect tllflllllitgfl of the filaments of the lamp through the spaces between or about said filaments, whereby a unrfiirm patch othght t'ree from the image of said filamentsis directed a gainst the opaque film;

3. In a cinematographic apparatus ot the character des'cribed; the combination with means tor feedinganopa-que =filmand a'proectmg lens, ofan-optical system'embodying therein a lamp havinga plurality o'f'spaced filaments,acondenser, abi-convex lens positioned at about the toeal point of the condenser and between said condenser and the teeding means torthe film th'erelative position of said bi-convexlensand said feeding means-being such: as to bring a; film upon saiduneans Where it will not be'at the image pOlI1t Of?S{L1( /l l6n$, a reversmgyprism having a reflecting surface provided with reflectmgmedmm,:arranged 1n-the path of the screen, and a spherical reflector positioned light: rays passing from the film to the" with relation to said lamp on the side there- In testimony whereof I have signed my of opposite to said condenser and s0 adname in the presence of two subscribing 10 justeil as to reflect the image of the filaments Witnesses.

of the lamp throu h the spaces between or r T T i 1 about said filameiits, whereby a uniform MARI'IB ALBERT JOHA HARPER patch of light free from the image of said Witnesses: filaments 1s directed against the opaque ALBERT EDGAR ALEXANDER, film.

CEeILm lVINlFRED Rownnnnn. 

